Listen for your tires.
Seriously. Any time your tires are squealing, you're losing time. Hit the brakes earlier and softer, and you should be able to get back on teh gas before the turn even starts.
Take a look at your replay, and compare it to the demo. You'll notice,that the demo uses much smoother and even inputs.
I had the most trouble between t1 and t2. A smoother turn through the tight left, amounts to so much more speed to be carried through the second and third tunnel, amounting to a better run across the back stretch.
Study the demo, as it will give you a number of clues on taking corners. With such a low powered car, you need to conserve momentum.
Good luck,
AO